Signal generator method and apparatus



Sept. 19, 1967 J. HAIMSON SIGNAL GENERATOR METHOD AND APPARATUS Filed Aug. 18, 1964 2 Sheets-Sheet 1' VI mw E N E R V A m 3 3 mH/Mm B o y C M N ZOZbmm ZOCbuw mwhuim ww Ia zOmhmrJx .SQhDO 443G hm mp 19, 1967 J. HAIMSON 3,343,101

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ATTORNEY 3,343,101 SIGNAL GENERATOR METHOD AND APPARATUS Jacob Haimson, Palo Alto, Calif., assignor to Varian Associates, Palo Alto, Calif., a corporation of California Filed Aug. 18, 1964, Ser. No. 390,320 15 Claims. (Cl. 331-82) The present invention relates in general to the production of high power radio frequency signals and particularly to a method and apparatus for producing high power signals utilizing charged particles accelerated to rela tivisttic velocities.

There is an ever present need for more powerful microwave signal generators. Presently the most advanced system proposed for producing outputs at the hundreds of megawatts level and higher is the use of an array of microwave tubes such as, for example, traveling wave tubes with the output signals from all of the tubes phased together to produce a single powerful output signal. The arrangement of such arrays and particularly the accomplishment of the desired phase relationship between each tube and every other tube of the array create many problems in both the electrical and mechanical construction of the phased array.

The object of the present invention is to provide a method and apparatus for producing powerful microwave signals in a construction which minimizes the adjustment parameters of the system and permits generation of the necessary output powers with a minimum of critical parts and assemblies.

Broadly stated, the present invention, to be described in greater detail below, is directed to the utilization of a particle accelerator and preferably an electron linear accelerator for accelerating charged particles to relativistic velocities and associated high energies and the passage of these high energy particles through a previously unexcited loaded output circuit in which a high power microwave signal is generated.

In the preferred practice of the present invention, microwave energy is stored in a first circuit such as the slow wave structure of an electron linear accelerator over a given pulse length approximately equal to the fill time of the structure such that the stored energy U in the circuit is equal to the product of the input microwave pulse power P and the circuit fill time T where a is a small correction due to circuit copper loss. A substantial portion such as, for example, one-half, of this stored energy is extracted by switching the circuit or dumping the circuit with a beam pulse directed therethrough and having a time duration substantially less than the fill time of the circuit such as, for example, T Consequently the beam emerging from this first section contains a substantial portion of the input microwave energy or in the particular example given the beam energy U is given by U /ZP XT XOL However, this energy is-concentrated in a short pulse: in this example a pulse of duration T /ZO. Therefore, since the peak power of the beam P is the ratio of the energy to the time duration, the beam peak power P is represented by the following:

As can be seen, the peak power of the beam can be one or more orders of magnitude greater than the input microwave peak power. In the case where the input power P is 20 megawatts the emerging beam power P can be on the order of hundreds of megawatts. The energy in United States Patent 3,343,101 Patented Sept. 19, 1967 the short beam pulse is then transferred back intoa microwave signal in the output circuit which is designed to build up induced RF output signal powers in a very short time, i.e., comparable to the beam pulse length and hence generate short RF pulses at peak powers far in excess of the peak powers of the input RF signal. Where the conversion efficiency from beam power to induced output signal power is on the order of the output signal pulses from the example given above will have powers in the hundreds of megawatts range. With this invention it may be possible to obtain output powers fifty times the input powers for very short beam pulse lengths.

One advantage of the present invention lies in the fact that high pulse powers can be generated in a structure aligned along a single beam path, thereby facilitating construction of the pulse generator and the combination of the generator and its load together.

Another feature of the present invention lies in the fact that the multimegavolt beams utilized in the production of the high power output signals can be produced and maintained without difficulty, thereby avoiding the problems encountered in providing for the necessary high DC potentials in conventional types of electron discharge devices of suflicient power to produce powers of the order produced with the present invention.

Additionally, in accordance with the present invention, it is possible to amplify peak pulse power by using the relativistic beam as a transfer mechanism to time compress the input signal or greatly reduce the pulse time of the input signal with respect to the output signal for maintaining a large portion of the input signal energy during the output signal pulse. In this way the power level of the output signal is far in excess of the power level of the source or sources which feed energy into the accelerating structure. Typically by utilizing input micro: wave pulses with durations on the order of microseconds and powers on the order of tens of megawatts it is possible with the present invention to produce output pulses with durations in the nanosecond range and powers in the range of hundreds of megawatts.

In accordance with the present invention the output circuit is a relatively low Q structure in which the induced RF signal can build up rapidly in order to effectively extract maximum energy from the short beam pulse. One arrangement for such an output circuit or portion thereof is the use of a low Q high group velocity linear accelerator type of waveguide which is dimensioned for optimum transfer of energy from the pulse of charged particles to the circuit.

An advantage of this output circuit lies in the fact that the circuit need not be as precisely tuned as normal linear accelerating structures and the detuning effects on such an output circuit by the high current beam which would normally be deleterious to the operation of such a structure used for acceleration can be tolerated when it is desired to induce an output radio frequency signal.

A number of different structures can be utilized for the output circuit and operating to induce either a forward or backward traveling wave. This structure can be a traveling wave circuit of coupled cavities in which accumulated power is extracted from the circuit at one end or the other or can be extracted at various points therealong. Also the circuit can be made up of a series of uncoupled cavities which are each properly coupled to a common output waveguide for producing a coherent output signal.

An additional feature of the present invention is the provision that the voltage of the beam entering the output structure be slightly greater than the voltage drop through the structure for the operational value of beam current in order to maintain the pulse of charged particles at relativistic velocity throughout traversal of the output circuit,

thereby avoiding loss of coupling due to debunching of the pulse and beam interception by the circuit.

As still an additional feature of the present invention, if appreciable reduction in velocity of the charged particles occurs in the output section the output section can be provided with a reduced phase velocity propagating characteristic, thereby to maximize the peak power RF output.

Still an additional feature of the present invention is the provision of an array of beam paths in each of which short pulse lengths of particles are accelerated to relativistic velocities and then introduced into an output circuit structure for inducing an output signal and with the separate output signals from the separate beam paths phased in a desired manner to produce a desired output signal.

An advantage of the use of a plurality of beam paths in accordance with the present invention lies in the fact that when the outputs from the several beam paths are combined in phase an extremely high output signal can be produced. On the other hand, by staggering the beam pulses within the separate beam paths a considerably increased output pulse repetition rate can be achieved.

Still another feature of the presentinvention is the provision of variations in the output circuit of the high power signal generator for maximizing the output signal. This can include a circuit with a reduction of phase velocity in the direction of the decelerating particles or a variation of impedance in the direction of the particles traveling therethrough.

Still another feature of the present invention is provision for programming the phase of arrival of the injected pulse of electrons into the accelerating section with respect to the crest of the traveling wave introduced into the section to produce an improved particle energy distribution in the accelerating structure.

Other features and advantages of the present invention will become more apparent upon a perusal of the following specification taken in connection with the accompanying drawings wherein:

FIG. 1 is a schematic view, partially in section and partially in block diagram form showing a structure for accomplishing the present invention;

FIG. 2 is a schematic view of an alternative embodiment of the present invention;

FIG. 3 is a schematic view of still another embodiment of the present invention;

FIG. 4 is a schematic view of still another embodiment of the present invention;

FIG. 5 is a schematic view illustrating one variation that can be made in the output circuit of the signal generator;

FIG. 6 is a schematic view of the output circuit of the signal generator provided with still another variation; and

FIG.7 is a graph showing energy of the particles in the pulse leaving the accelerating section of the signal gen erator plotted versus time and illustrating achievement of an improved energy relationship.

Referring now to FIG. 1, there is shown a high power signal generator generally indicated as 10 in accordance with this invention and including a plurality of first or input electromagnetic waveelectron beam interaction structures 11 in which energy is transferred from an electromagnetic wave to a short pulse of charged particles, thereby accelerating them to relativistic velocities, a second interaction structure 12 in which energy in transferred from this short pulse high energy charged particle beam to the structure, thereby inducing a short pulse high peak power output signal, a source of microwave frequency power 13 for energizing each of the firstwave-beam interaction structures 11 and a source 14 of charged particles which are first directed in a short pulse through the first interaction structures 11 for gaining energy, then through the second interaction structure 12 to produce a high power output signal which is directed through an output coupling 15 to a load (not shown), the particles passing from structure 12 into a beam collector 18.

The signal generator 10 is preferably formed with a.

single vacum envelope 16 extending the length of the beam path and which is provided with the pulsed source of particles 14, at one end, the output interaction circuit 12 at the other end, and the input interaction structures 11 located between the beam source 14 and the output circuit 12. The beam pulse generator 14 includes a particle gun such as, for example, an electron gun assembly 20 comprising a cathode and focus electrode subassembly 21 and an apertured anode 22. A pulsed voltage is applied between the cathode 21 and the anode 22 for creating a pulsed electron beam 23 which is focused along the beam path through an aperture in the anode 22 into a deflector assembly 24.

The deflector assembly 24 includes a focusing lens 25 such as, for example, a thin magnetic lens coil spaced along the beam path from the anode 22 for focusing the diverging pulsed electron beam 23 onto or through an axially alined collimating aperture26' in a collector 26. A first pair of deflection plates 27 and 28 are located on opposite sides of the beam path between the anode 22 and the lens 25 for deflecting the pulsed electron beam 23 from a position in which the beam impinges on the collector 26 to a position for passage through the collimating aperture 26 in the collector 26. A second pair of deflection plates 29 and 30 are located between the lens 25.

and the collector 26 for deflecting the electron beam from the position in which it passes through the collimating aperture 26 to a position for impingement on the collector 26. The second pair of plates29 and 30 is rotated with respect to the pair 27 and 28 to allow for the rotation imparted to the beam in passing through the lens 25. A magnetic bias field. is produced in the region between the second pair of plates 29 and 30 by coils located on the side of the deflecting assembly 24 to counterbalance the electric field between the plates so that for operation of the deflection assembly, as described in greater detailbelow, one of the plates can be grounded, thereby avoiding problems of voltage variation on the plate and variation in the field strength between the plates due to beam interception.

The electric field between each pair of deflection plates can be separately controlled, as will be described'in greater detail below, for deflecting the electron beam between a position off the axis of the envelope 16 for collection on the collector 26 to a position on the axis of the en velope 16 for passage through the collimating aperture 26' into the accelerating structure. In this manner an easily adjustable short pulse of electrons can be passed through the collimator 26 into a prebuncher 31 which causes the beam to be bunched. The bunched beam is focused to a small diameter by means of, for example, a thin magnetic lens coil 32 and directed into the input end of the first Interaction section 11.

The input or first wave-beam interaction structures 11 are preferably typical traveling wave linear accelerator sections composed, for example, of a series of coupled cavities arranged along the beam path and formed by disc loaded waveguide with coupling apertures in the discs for passing the pulse of charged particles and accelerating the pulse of charged particles withenergy from the electric fields established within the structure by microwave energy introduced into the accelerator sections from the source 13. Typically, the first of the input sections 11 includes an initial variable phase velocity buncher section made up of a plurality of cavity resonators for initially propagating the microwave signal with a steadily increasing phase velocity and wavelength and a subsequent constant phase velocity section for propagating the microwave signal at substantially the velocity of light. The microwave energy is introduced into each'of the input sec.- tions 11 from the source 13 which can be, for example, a multiple output klystron with the second output phased by a phase shifter 37 such that the applied microwave sig nal transfers energy in an optimum manner to accelerate the beam. Residual microwave energy at the end of each of the sections 11 is coupled through an output coupling 35 to an RF load 36.

Purely by way of illustration the input sections 11 have been shown schematically as separate assemblies, but in practice since extended sections may be desired the input or first wave-beam interaction structure 11 could be one continuous length of accelerating waveguide with microwave power introduced therein from one or more microwave tubes, or by using RF recirculating techniques.

The accelerated short pulse of electrons from the output of the last input section 11 is introduced into an initially unexcited output section 12 which is shown, by way of example, as a disc loaded waveguide composed of a series of cavity resonators coupled together by axially aligned apertures through which the beam is also passed. The resonators are tuned to have a phase velocity substantially equal to the beam velocity at the fundamental frequency and dimensioned such that an electromagnetic wave is induced in the interaction structure 12 as the beam is passed therethrough. The decelerated particles are then collected either inside the vacuum envelope 16 or in collector 18 outside the envelope after passage through a vacuum window 17. Typically the interaction structure 12 has a low Q and/or high group velocity so that RF fields can build up rapidly in the structure 12 commensurate with the short pulse length of the beam, and if the output circuit and the beam are adequately matched, a large fraction of the energy of the pulsed particle beam can be transferred to the circuit in the course of the beam passage therethrough.

In the preferred embodiment of the invention the beam voltage at the entry of the output interaction structure 12 is greater than the voltage loss due to energy transfer in the structure so that the beam remains at substantially relativistic velocity during passage therethrough so as to avoid loss of coupling between the beam and the circuit due to debunching of the beam with reduction in velocity and to minimize beam interception by the circuit. The wave induced in the output section is coupled out of the traveling wave structure illustrated in FIG. 1 via the coupling to a load such as, for example, an antenna (not shown).

Operation of the method and apparatus in accordance with the present invention will be describedwith a typical operating example which is by no means optimum. A pulsed electron beam is produced in the electron gun 20 having a pulse duration of approximately one microsecond with a peak beam current of approximately 20 amps. In the deflector assembly 24 the deflection plate 28 is grounded and deflection plate 27 is held at a potential of approximately 10 kv. Similarly, the deflection plate is grounded and deflection plate 29 is held at a positive potential of approximately 10 kv. The particle deflection in the region of the second pair of plates 29 and 30 due to the electric field between those plates is counterbalanced by the magnetic field supplied by the coils 38. The positively charged deflection plates 27 and 29 are coaxially connected to thyratrons which may be independently triggered to provide control of the Start and Stop of the transmitted beam pulse as described below. During the initial portion of the pulse deflection plates 27 and 29 are positively charged such that the diverging beam passing between the firstpair of plates is radially deflected from the axis of the deflection assembly, passes through the thin lens field where some image rotation is produced, and is focused on the surface of the collector 26 radially displaced from the centrally located collimating aperture 26'. No deflection action is experienced by the converging beam in passing through the second pair of plates 29 and 30 because of the biased field condition. When the first inflector plate is rapidly discharged by triggering its driver thyratron the beam suddenly becomes symmetrically lo cated about the center line of the deflection system causing the focal point to sweep along the surface of collector 26 into the collimating aperture 26 and provide injection into the accelerating structure. After expiration of the desired time delay, inflector plate 29 is discharged by its thyratron and the DC magnetic bias field remaining in the region between the second set of plates causes the beam to be deflected away from the collimating aperture 26' and swept onto the collector 26. This system enables variable beam pulse length, such as on the order from microseconds to nanoseconds, to be easily obtained by selection of the start and stop thyratron trigger phase de lays. In the operative example, a 20 nanosecond pulse is passed through the low Q prebuncher cavity 31 for bunching of the beam and then into the first of the input sections 11 for acceleration of a peak current'of approximately 10 amps to relativistic velocity.

Before the pulse is introduced into the accelerating section 11 microwave energy at S band frequency is coupled into the input accelerating sections 11 (as well as the prebuncher cavity) from the source 13 for a fill time period such as, for example, approximately /2 microsecond long, thereby storing energy in the input sections 11. The short high current pulse of electrons extracts a substantial portion of this stored microwave energy such as, for example, approximately 50%, and is accelerated to relativistic velocities. With two input sections each approximately meter long and fed by a microwave signal having a pulse length greater than /2 microsecond at an input power level of 10 megawatts per section, the electrons in the initial portion of the short pulse are accelerated to relativistic velocity and energy on the order of 15 mev. dropping to approximately 10 mev. at the end of the pulse. Residual RF power at the end of the accelerating sections is dissipated in the loads 36.

As the high energy short pulse electron beam passes through the output section 12, energy is transferred from the electrons to the circuit to set up fields in the section 12 thereby to induce an RF signal in section 12 which is coupled out of the output section 12 via the line 15 to a load such as, for example, an antenna. The residual energy pulse of electrons is passed through an output window 17 and into collector 18 or for subsequent measurement and/ or application. In the actual operation of a system according to this example and wherein no elfort was made to maximize the output signal produced but only to produce a signal, the peak output signal produced in the output tube circuit 15 was on the order of 5 megawatts. Outputs in the range of hundreds of megawatts can be expected if the system is constructed and tuned for maximum efiiciency.

Refer-ring now to FIG. 2, there is shown schematically an alternative out-put structure 12 which includes a plurality of short traveling wave circuits 12', each of which is coupled to an output circuit 15' and properly phased with respect to the output signals from the other of the circuits 12' to produce a phase coherent output signal. While each of the traveling wave circuits 12 is shown schematically as a short disc loaded waveguide, other configurations can be used such as, for example, other coupling apertures in the discs or other means for coupling the adjacent cavity resonators making up each of the circuits 12'.

It is also possible, as schematically shown in FIG. 3, to couple the energy from each of the individual cavity resonators 55' to a common output waveguide 56 connected to the load so that the output circuit is then effectively a series of separate standing wave cavity resonators for producing a portion of the output signal directly from each of the cavity resonators 55 rather than producing the signal via a growing traveling wave. The output waveguide 56 is phase tuned properly to combine the individual cavity outputs.

Referring now to FIG. 4, there is shown an alternative arrangement for producing a high power output signal which consists of a plurality of beam paths 50 in each of which particle acceleration and output signal generation takes place and with the output signals produced in the separate output circuits 12 coupled together to produce a high power output signal. The output signals from the separate beam paths can be combined to produce a signal having desired characteristics. For example, the separate signals can be added in phase to produce a higher power output signal or the separate signals can be added partially out of phase or coded to produce coded output signals. Because of the extreme smiplicity of triggering the short electron beam pulses, coded RF peak power nanosecond pulses can be easily produced from multiple beam paths.

The efficiency of the output circuit can be improved slightly by either providing the circuit of the output section with a reduced phase velocity, such as, for example, changing the space between waveguide loading elements 60 in the output circuit 61 as shown in FIG. 5, or by providing the output circuit with a high initial impedance and then varying, for example decreasing, the impedance in the direction of the beam travel, which can be accomplished by well known-techniques such as, for example, enlarging the output waveguide 70 as shown schematically in FIG. 6.

Alternatively, other circuits which combine the properties of fast response and high shunt impedance may be utilized, e.g., backward wave circuits, ring-and-bar loaded circuits, jungle gym circuits, etc.

Normally, the high energy short pulse beam produced at the end of the input or accelerating section will have an energy degradation approximately linear with pulse time due to the continual extraction of energy from the input section so that the subsequent bunches of elec-.

trons in the pulse experience an ever decreasing electric field gradient. This energy curve with pulse time is shown by the dotted line 80 in FIG. 6. Consequently, in the limit, the maximum beam charge during stored energy operation of the accelerating section is determined by the allowable energy spectrum from the apparatus. By programming the phase of arrival of the injected pulse of electrons into the accelerating section with respect to the crest of the traveling wave introduced into the section it is possible to obtain a compromise between reduction in the electric field within the accelerating waveguide due to beam loading depletion of stored energy of the waveguide with time and phase migration of the electron bunch into a region of high electric field. This technique combined with the replenishment of RF power in the first few cavities of the accelerating structure during the short pulse will enable achievement'of a more uniform energy spectrum for the pulse output as shown in FIG. 6 by the solid line 81. The programmed. arrival of particles into the accelerating section can be accomplished in a number of ways; for example, a 'prebuncher drive phase shifter can be varied, a ramped voltage can be provided on a drift space electrode assembly, or a variation can be provided on the particle gun.

An important feature of the present invention=is the utilization of short high current pulses. While the invention has been described with the respect to the utilization of a deflection plate assembly for sweeping the beam into and out of the aperture in the beam collimator to produce these pulses, other systems can be utilized and may be necessary for production of extremely high current pulses such as, for example, 100 amperes. By way of example, other structures and systems that may be used are a gridded particle gun, microwave beam sweeping techniques, microwave particle bunch selection and compression techniques, and short pulse discharge circuits for voltage pulsing a hot cathode or temperature pulsing an energized cathode with a laser beam.

While, operation of the pulse generator has been described with respect to injection of the pulse of charged particles into the accelerating structure duringcontinual application of power from the RF source, it is possible to cut off the RF power delivered to the accelerating structure (especially for high Q lower frequency circuits) before the pulse of charged particles is introduced into the accelerating structure.

While the invention has been described thus far with particular reference to the use of electrons as the charged particles for generating the output signal, it is obvious that under certain circumstances other charged particles can be used.

Since many changes could be made in the above construction and method and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. Apparatus for generating high power microwave energy comprising a wave-beam interaction structure provided with means for passing a beam of charged particles therethrough and for establishingelectromagnetic wave energy fields in the regions through which said beam of charged particles passes;

means for coupling input electromagnetic wave energy of high power into said wave-beam interaction structure for establishing said electromagnetic fields within said wave-beam structure;

an output circuit structure provided with means for passing a charged particle beam therethrough and dimensioned for causing particles passing therethrough to induce an output electromagnetic wave signal within said structure;

means for generating a beam of charged particles and directing said beam into and through said wave-beam interaction structure;

said wave-beam interaction structure constructed and dimensioned to provide an accelerator for transferring a substantial portion of said input electromagnetic Wave energy to said beam of charged particles; netic wave energy to said beam of charged particles to accelerate said particles to a velocity substantially in excess of their velocity upon entering said wavebeam interaction structure; and

means for directing said beam of accelerated particles into said output circuit structure thereby to induce said output electromagnetic wave signal in said output, circuit structure;

2. Apparatus for generating a high power pulsed microwave signal comprising a Wave-beam interaction structure produced with means for passing a pulse of charged particles therethrough and for establishing electromagnetic wave energy fields in the regions through which said pulse of charged particles passes;

means for coupling input electromagnetic microwave energy into said wave-beam interaction structure for establishing said electromagnetic fields within said wave-beam structure;

an output circuit structure provided with means for passing a pulse of charged particles therethrough and constructed and dimensioned for causing said pulse to induce an output electromagnetic wave signal 1 within said circuit structure;

means for generating a pulse of charged particles and directing said pulse into and through said wave-beam interaction structure;

said wave-beam interaction structure constructed and dimensioned for transferring said input electromagnetic wave energy to said pulse of charged particles to accelerate said particles to relativistic velocity;

means for'directing said pulse of accelerated particles into said output circuit structure thereby to induce said output electromagnetic wave signal in said output circuit structure; and

means for coupling said induced output signal from said output circuit structure to a load.

3. Apparatus for generating high power signal comprising a high Q electromagnetic wave propagating structure for establishing electromagnetic wave energy fields therein in response to applied electromagnetic wave energy, said high Q structure provided with means for passing charged particles therethrough in said electromagnetic fields to transfer energy from electromagnetic waves applied to said high Q structure to charged particles passing therethrough;

means for coupling electromagnetic wave energy into said wave propagating structure for establishing electromagnetic fields within said wave propagating structure;

a low Q electromagnetic wave generating structure provided with means for passing charged particles therethrough for inducing electromagnetic wave energy therein; 1

means for generating and directing into said high Q structure a "beam of charged particles such that a substantial portion of energy from the electromagnetic fields within said high Q structure is transferred to said charged particles; and

means for directing the increased energy charged particles into said low Q electromagnetic wave generating structure to produce therein a high power electromagnetic signal.

4. Apparatus for generating high power pulsed microwave signal comprising a high Q electromagnetic wave propagating structure for establishing electromagnetic wave energy fields therein in response to applied microwave electromagnetic wave energy, said high Q structure provided with means for passing charged particles therethrough in said electromagnetic fields to transfer energy from electromagnetic Waves applied to said high Q structure to charged particles passing therethrough;

means for coupling microwave electromagnetic wave energy into said wave propagating structure for establishing electromagnetic fields within said wave propagating structure over a certain time interval;

a low Q electromagnetic wave generating structure provided with means for passing charged particles therethrough for inducing electromagnetic wave energy therein;

means for generating and directing into said high Q structure a pulse of charged particles having a pulse duration less than said certain time interval to transfer a substantial portion of energy from the electromagnetic fields within said high Q structure to said pulse of charged particles; and

means for directing the increased energy pulse of charged particles into said low Q electromagnetic wave generating structure to produce therein a high power pulsed mocrowave electromagnetic wave.

5. Apparatus for generating high power pulsed energy comprising;

a high Q electromagnetic wave propagating structure for propagating an electromagnetic wave in a given frequency range, said wave propagating structure provided with means for passing a pulse of charged particles therethrough for interaction with electromagnetic Wave energy therein for acceleration of said charged particles;

means for coupling electromagnetic wave energy in said frequency range into said wave propagating structure for establishing electromagnetic fields after a given fill time for acceleration of charged particles therethrough;

a low Q electromagnetic wave generating structure provided with means for passing accelerated charged particles therethrough for inducing electromagnetic wave energy therein;

means for generating and directing into said high Q structure a pulse of charged particles having a plus duration less than said certain time interval to transfer a substantial amount of stored energy from the electromagnetic fields within said high Q structure to said pulse of charged particles to accelerate said particles to relativistic velocity; and

means for directing said pulse of accelerated particles into said low Q structure wherein said pulse of particles is slowed to produce a high power pulsed electromagnetic wave in said low Q structure.

6. Apparatus for generating high power short pulse energy comprising;

a first wave-beam interaction structure provided with means for passing a charged particle beam therethrough and dimensioned for transferring energy from an input electromagnetic wave in said inter action structure to charged particles passing therethrough;

means for coupling an input electromagnetic wave to said first structure to set up electromagnetic fields within said first structure over a prescribed time interval;

a second wave-beam interaction structure provided With means for passing a charged particle beam therethrough and dimensioned for causing said charged particles passing therethrough to induce an output electromagnetic wave within said second structure;

means for producing a pulse of charged particles with the time duration of the pulse less than said prescribed time interval for setting up electromagnetic fields in said first wave-beam interaction structure;

means for directing said pulse of charged particles through said first wave-beam structure to transfer stored energy from said wave to said particles for extracting a substantial portion of the energy stored in said first wave-beam interaction structure during said prescribed time interval into the duration of said pulse thereby to produce a high power particle pulse; and

means for directing said high power pulse of charged particles through said second wave-beam interaction structure to induce saidoutput electromagnetic waves in said second wave-beam interaction structure with high peak powers and a pulse length substantially that of said pulse of charged particles.

7. Apparatus for generating high power short pulse energy comprising:

a first wave-beam interaction structure provided with means for passing a charged particle beam therethrough and dimensioned for transferring energy from an electromagnetic wave in said interaction structure to charged particles passing therethrough, to accelerate the charged particles to relativistic velocity;

means for coupling an input electromagnetic wave to said first structure to store energy in electromagnetic fields within said first structure over a prescribed time interval;

a second wave-beam interaction structure provided with means for passing a charged particle beam therethrough and dimensioned for causing said charged particles passing therethrough to decelerate and induce an output electromagnetic wave within said second structure;

means for producing a pulse of charged particles with the time duration of the pulse less than said prescribed time interval for setting up electromagnetic fields in said first wave-beam interaction structure;

means for directing said pulse of charged particles through said first wave-beam structure for accelerating particles with stored energy from said input electromagnetic wave; and

means for directing said accelerated pulse of charged particles through said second wave-beam interaction structure for decelerating said particles and inducing an output electromagnetic wave in said second wavebeam interaction structure.

8. The apparatus in accordance with claim 7 characterized further in that said first wave-beam interaction structure is a traveling wave linear accelerator for accelerating said pulse of charged particles to substantially relativistic velocity.

9 Apparatus for generating high power short pulse energy comprising:

a first wave-beam interaction structure provided with means for passing a charged particle beam therethrough and dimensioned for transferring energy from an output electromagnetic wave in said interaction structure to charged particles passing therethrough;

means for coupling an input electromagnetic wave to said first structure to set up electromagnetic fields within said first structure over a prescribed time interval;

a second wave-beam interaction structure provided with means for passing a charged particle beam therethrough and dimensioned for causing said charged particles passing therethrough to transfer energy from said charged particles to said structure to induce an output electromagnetic wave within said second structure;

means for producing a pulse of charged particles with the time duration of the pulse less than said prescribed time interval for setting up electromagnetic fields in said first wave-beam interaction structure,

means for directing said pulse of charged particles through said first wave-beam interaction structure such that a substantial portion of the electromagnetic wave energy stored in the electromagnetic fields within said first wave-beam interaction structure is transferred to said pulse of charged particles to accelerate said pulse of charged particles to substantially relativisticvelocity; and

means for directing said accelerated pulse of charged particles through said second wave-beam interaction structure for decelerating said particles and transferring a substantial portion of the energy of said charged particles to said second wave-beam interac- 12 tion structure to produce a high power electromagnetic wave.

10. The apparatus in accordance with claim 9 characterized further in that said first wave-beam interaction structure is a traveling wave linear accelerator for accelerating said pulse of charged particles to substantially relativistic velocity.

11. The apparatus of claim 9 including a plurality of beam paths each including first and second wave-beam interaction structures, and means for directing a pulse of charged particles successively therethrough and means for combining the high power electromagnetic waves induced in said second wave-beam interaction structures to produce a single high power output signal.

12. The apparatus of claim 9 characterized further in that said second wave-beam interaction structure includes means for reducing the electromagnetic wave phase velocity in the direction of beam travel therethrough.

13. The apparatus of claim 9 characterized further in that said second wave-beam interaction structure includes means for varying the impedance thereof in the direction of beam travel therethrough.

14. The apparatus of claim 9 including means for programming the introduction of the particles of said pulse into said first wave-beamtinteraction structure to produce substantially uniform energy particle over the length of the pulse for direction through said second wave-beam interaction structure.

15. A method for producing high energy radio fre quency pulses comprising the steps of storing microwave energy in a particle accelerating structure; ac-

celerating to substantially relativistic velocity a pulse of charged particles having a pulse duration less than the fill time of said accelerating structure for said radio frequency energy and inducing an output high power radio frequency pulse with said accelerated pulse of charged particles.

No references cited.

ROY LAKE, Primary Examiner.

JOHN KOMINSKI, Examiner. 

1. APPARATUS FOR GENERATING HIGH POWER MICROWAVE ENERGY COMPRISING A WAVE-BEAM INTERACTION STRUCTURE PROVIDED WITH MEANS FOR PASSING A BEAM OF CHARGED PARTICLES THERETHROUGH AND FOR ESTABLISHING ELECTROMAGNETIC WAVE ENERGY FIELDS IN THE REGIONS THROUGH WHICH SAID BEAM OF CHARGED PARTICLES PASSES; MEANS FOR COUPLING INPUT ELECTROMAGNETIC WAVE ENERGY OF HIGH POWER INTO SAID WAVE-BEAM INTERACTION STRUCTURE FOR ESTABLISHING SAID ELECTROMAGNETIC FIELDS WITHIN SAID WAVE-BEAM STRUCTURE; AN OUTPUT CIRCUIT STRUCTURE PROVIDED WITH MEANS FOR PASSING A CHARGED PARTICLE BEAM THERETHROUGH AND DIMENSIONED FOR CAUSING PARTICLES PASSING THERETHROUGH TO INDUCE AN OUTPUT ELECTROMAGNETIC WAVE SIGNAL WITHIN SAID STRUCTURE; MEANS FOR GENERATING A BEAM OF CHARGED PARTICLES AND DIRECTING SAID BEAM INTO AND THROUGH SAID WAVE-BEAM INTERACTION STRUCTURE; SAID WAVE-BEAM INTERACTION STRUCTURE CONSTRUCTED AND DIMENSIONED TO PROVIDE AN ACCELERATOR FOR TRANSFERRING A SUBSTANTIAL PORTION OF SAID INPUT ELECTROMAGNETIC WAVE ENERGY TO SAID BEAM OF CHARGED PARTICLES; TO ACCELERATOR SAID PARTICLES TO A VELOCITY SUBSTANTIALLY IN EXCESS OF THEIR VELOCITY UPON ENTERING SAID WAVEBEAM INTERACTION STRUCTURE; AND MEANS FOR DIRECTING SAID BEAM OF ACCELERATED PARTICLES INTO SAID OUTPUT CIRCUIT STRUCTURE THEREBY TO INDUCE SAID OUTPUT ELECTROMAGNETIC WAVE SIGNAL IN SAID OUTPUT CIRCUIT STRUCTURE. 